There a simple filter for Template::Toolkit (Template::Plugin::HTML::Template) that will allow HTML::Template like objects. As for a HTML::Template <-> Template::Toolkit converter that shouldn't be too hard to write, at least for most basic functions. Though I too wonder why you would need this; esp. since a number of function just don't exist in HTML::Template so you'll have to write those anyway should be a simple matter to also convert.

TThanks Kutsu:
The filter, you mentioned, is useful to me. I like to convert my templates so I can use them with 'Template Toolkit' which has more functionality. I wanted to convert because I can put more stuff into templates in future. I think that, you thought the other way around.